Variable wheel base vehicle

ABSTRACT

A variable wheel base vehicle includes a vehicle body having front end rear ends supporting body members one of which is capable of displacement relative to the other. Drive motors mounted to the vehicle body are linked to the body members. A carriage assembly including drive wheels provide support for the vehicle body. An extension assembly responsive to the drive motor is connected to at least one of the body members. Upon actuation of the drive motor, the extension assembly enables one body member to displace relative to the other body member to enable extension and retraction of the vehicle wheel base. Each body member includes at least one wheel of the carriage assembly and, as a result of displacement of one body member relative to the other body member, the displaced body member provides increased counterbalance in the vehicle.

BACKGROUND

The present invention relates to motor vehicles and particularly, thoughnot exclusively to vehicles capable of performing heavy duty workfunctions such as loading and more particularly relates to improvementsin the construction, operation and stability of such vehicles. Moreparticularly the invention relates to a variable geometry vehiclewherein at least the wheel base can be extended to provide acounterbalance for loading which would otherwise tend to destabilise thevehicle. Whilst the present invention will be described primarily withreference to skid steer vehicles, it will be understood by personsskilled in the art that the invention is not limited to vehicles able toperform loading functions but is applicable to a wide variety ofvehicles capable of performing functions other than loading.

PRIOR ART

There are in existence a number of different types of loaders eachdesigned to perform the functions of lifting and loading. Theconfigurations of the known loaders are largely dictated by the functioneach performs. Among the known loaders are skid steer loaders, forklifts, front end loaders and backhoes with the latter having front endloading capability.

Skid steer loaders are well known vehicles which generally comprise, avehicle body of monocoque construction having drive means mounted in oron the body, two sets of wheels attached to and supporting the body anda work implement such as a front end loader assembly attached to thevehicle body. The skid steer loader was developed as a very compact,relatively light and very manoeuvrable vehicle. It is therefore able tobe transported in small tippers to building and work sites and is veryuseful in confined areas providing reasonable pushing and loadingability. One such skid steer loaders having a very short wheel base hasproven to be successful as an easily transportable earth mover capableof detachably receiving a variety of work implements and in being ableto do so replacing larger and more expensive machines eg. (backhoes,diggers, etc.) Despite these advantages these skid steer loaders areknown to be inherently unstable in operation. As they are short wheelbase vehicles, they rely to some extent for operational stability on theweight of the drive assembly, particularly the motor, which is generallymounted rearward to provide counterbalancing for the front end workimplement and, in view of the overall geometry of the machine, it musttherefore adopt a balance compromise. Thus, if the rear of the machineis weighted too heavily for the purpose of allowing a large payloadbucket lift, the machine would rear up trying to negotiate minor slopesand obstructions particularly when the bucket is empty. Alternatively,if the rear of the machine was weighted too lightly, it would not lift areasonable payload and would be susceptible to forward rotation aboutthe front wheels.

Previously, skid steer loaders have needed to be rear heavy to liftweights and although not designed specifically for this purpose, toallow the machine to climb steep slopes backwards where necessary, andto allow pick up of a reasonable payload in the bucket during each lift.Rear weighting has thus proven to be the best possible compromise in avery short wheel base machine. Thus, when negotiating very steep slopesfor safety the existing short wheel base skid steer loaders arepreferably reversed up slopes where practical but are limited to onlymoderate slopes when travelling forward and when the bucket is emptyparticularly when the bucket is in the air.

The dynamic forces distributed over this machine in use are quitecomplex and along with the short wheel base contribute to the machinesinherent instability. The dynamic loads on the existing machines varyaccording to a number of factors taken separately or in combination withother factors which include; the speed at which the machine is drivenduring operation, the load carried in the loading assembly bucket, theheight of the bucket lift, the roughness of the terrain on which theloader is driven, the level of tire inflation, the severity ofacceleration and deceleration (or braking), the slope of the surface onwhich the machine operates and the heaving and lateral loads inducedwhen steering right or left.

An unskilled driver can easily create instability problems inadvertentlywhereby the machine can quite easily overturn. A skillful driver is onewho can constantly and speedily compensate for inherent instabilityproblems in the known short wheel base skid steer vehicles. This causesperformance of work functions by the machine to be much slower than theyotherwise could be were the machine more stable.

The existing skid steer vehicles are positively dangerous in some useoperations and configurations. For instance, where a load is liftedhigh, the potential for overturning of the machine is great and can beexacerbated by rapid deceleration. When the same load is carried lowdown the tendency for frontward overturning remains however, the loaderbucket will engage the ground before overturning occurs. Thus, when anoperator is carrying a load in the bucket it is strongly advisable tocarry the bucket near the ground as the machine is in thesecircumstances both laterally more stable and more able to counter thetendency towards overturning.

Skid steer loaders are known to be able to negotiate flat ground whenloading a truck. On moderate and steep slopes these loaders have beenknown to simply roll over backwards due to the change in balancedistribution during the loading and particularly the unloading phase.The need to constantly position the bucket low to improve the balancegeometry increases cycle time during loading and unloading. The enginein the known skid steer loaders is mounted rearward to provide arestoring moment to balance the effect of the overturning moment inducedin the machine by the loaded bucket. The above described phenomenon ismagnified where the operator is working on a forward or side slope.Also, rough terrain makes it very dangerous for the operator to operatesafely as there is an increased tendency for the machine to overturnforward, laterally or rearward.

When another working implement is attached to the above described skidsteer loaders such as a ditch digging implement, stability problems arestill manifest. Indeed, if the working implement weigh less than theaforesaid bucket, stability problems are exacerbated.

Another vehicle susceptible to instability is the conventional forklift. This commonly used loader generally comprises a drive assemblylocated in a body mounted on a wheel assembly or chassis or isalternatively of monocoque construction. The chassis includes a wheelassembly which defines a relatively short wheel base (though longer thanthat of the typical skid steer loader) and typically at the front of thevehicle there is a generally upright frame which supports a set oflifting forks able to travel in the vertical and/or horizontaldirection.

The forks in these vehicles usually lie well forward of the wheel basefootprint. Heavy loads applied to the forks induce forward rotation inthe vehicle about the front wheels. The heavier the load the greater thetendency for forward rotation. Unwanted rotation is to an extentcounterbalanced by the weight at the rear of the vehicle including thedrive motor. The fork lift operator must be skilful enough to ensurethat the machine is not loaded beyond capacity or driven in a way thatcompromises safety. Thus, the instability of the machine can result fromthe manner in which the machine is driven and the geometry of both theload and the machine. The potential for instability of this machine istaken into account when training fork lift operators. However, in someinstances it may be difficult to judge just how heavy a load is and thusto compensate adequately to avoid overturning laterally or forwards.There is therefore a need to enhance the stability of short wheel basevehicles including hereinbefore described but without compromise toexisting advantageous features in these vehicles.

As skid steer loaders are inherently unstable machines, due largely totheir short wheel base, the potential for accidental overturning of themachine during normal use is high. In response to this, manufacturershave examined the possibility of improving machine stability byincreasing the wheel base. However, due to the compact nature of thesemachines and the limited space in or on the vehicles to house anyadditional componentry which can enhance stability, the mechanicaloptions are very limited. Consequently, only small increases have beenmade to the wheel base in the order of 100 mm. In practice, the skidsteer concept necessitates a short wheel base to allow efficient turningability but an increase in wheel base length to increase stability.Thus, a fixed increase in wheel base compromises the machines ability toturn requiring additional horsepower. This also results in increasedtire wear. For these and other reasons manufacturers have beenrestricted to the small and fixed increase in wheel base.

The present invention seeks to overcome or at least ameliorate theaforesaid disadvantages of certain prior art vehicles particularlythough not exclusively skid steer and fork lift vehicles and withoutcompromise to the existing advantageous features of such vehicles byproviding a variable geometry vehicle with enhanced operationalstability characteristics and means to allow selective variation to thelength of the wheel base either during operation or whilst the vehicleis stationary.

According to one form of an apparatus aspect of the invention there isprovided a variable geometry vehicle having a vehicle body comprisingbody members at least one of which is adapted to extension andretraction relative to at least one other body member resulting inextension of the wheel base to thereby enhance the dynamic stabilityand/or balance geometry of the vehicle during operation.

In one broad form the present invention comprises:

-   -   a variable geometry vehicle able to move between a retracted        working configuration and an extended working configuration        wherein the extension and retraction is effected by means of at        least one hydraulic extension assembly integral with or        connected to the vehicle and wherein as a result of said        extension, the wheel base of the vehicle is increased. According        to a preferred embodiment the vehicle is either a fork lift or        skids steer loader.

In another broad form the present invention comprises:

-   -   a variable geometry vehicle comprising:        -   a vehicle body having front and rear ends and including body            members at least one of which is capable of displacement            relative to another body member,        -   drive means in or on said vehicle body operably linked to            one or more said body members,        -   a carriage assembly including drive wheels providing support            for the vehicle body,        -   an extension assembly responsive to the drive means and            connected to at least one of the body members, and which            upon actuation by said drive means enables one body member            to displace relative to another body member thereby enabling            extension and retraction of the vehicle's wheel base;        -   wherein each said body members include at least one wheel of            said carriage assembly, and        -   wherein as a result of said displacement of one body member            relative to another body member the displaced body member            provides increased counterbalance in the vehicle.

According to a preferred embodiment there are two body members whichtogether form the vehicle body each of which body members include twoindependently driven wheels and means enabling attachment of the bodymember to a member of said extension assembly such that actuation of theextension assembly causes longitudinal displacement of one body memberrelative to the other wherein the two independently driven wheels areintegral with and move with the displaced body member. Preferably, thedrive means includes a drive motor connected to and supported by thebody member which displaces thereby contributing to said counterbalance.

In the preferred embodiment the vehicle is a skid steer loader having asa work implement a front end loader assembly although other workimplements may be fitted to a vehicle having the extension facility suchas but not limited to lifting, digging, breaking, pushing or towingequipment.

In another broad form, the present invention comprises:

-   -   a variable geometry four wheel skid steer loader or fork lift        including in or on the body of the vehicle an extension assembly        which enables selective increase in the vehicle's wheel base        whilst stationary or during operation.

According to the preferred embodiment, the invention is applicable to askid steer loader of the type which comprises a vehicle body ofmonocoque construction, a drive means wherein the vehicle body ismounted on a wheel assembly wherein a part of the vehicle body is ableto move longitudinally relative to the remainder of the body. Theseparated components may be joined by one or more extension assembliesattached to the vehicle body. Each extension assembly may comprise atelescopic member of square or rectangular hollow steel section althoughit will be appreciated that other sections such as but not limited totriangular, elliptical or circular sections may be equally suited to thepurpose. The telescopic member has a fixed member and a moving memberwherein at least the fixed member is attached to the vehicle body and isactuated hydraulically by the vehicles hydraulic system or actuated by aself contained hydraulic system linked to the vehicle's motor. Theresult of the extension of the extension assembly is that the wheel baseis extended and the self weight and applied loadings forward of thefront wheel axis of the vehicle are counterbalanced.

In another broad form of the apparatus aspect the invention comprises:

-   -   an extension and retraction assembly for attachment to the body        of a variable geometry vehicle to enable one body member of said        vehicle to move longitudinally relative to another body member        thereby increasing the wheel base of the vehicle, the assembly        comprising:    -   at least one telescopic member having a fixed member fixedly        attached to one body member of the vehicle and a moveable member        which engages a moveable body member of the vehicle.

According to an alternative embodiment the telescopic member may includetherewithin a telescopic actuation cylinder.

In another broad form the present invention comprises:

-   -   an extension and retraction assembly for fitting to a vehicle        capable of performing a loading or other work function, the        assembly enabling the body of the vehicle to undergo selective        extension and retraction to alter the wheel base of the vehicle;    -   the assembly comprising:        -   at least one telescopic member having one sleeve member            fixed to one part of the vehicle and another moveable member            which engages another part of the vehicle wherein the            telescopic member includes therein a telescopic hydraulic            cylinder.

Preferably, the vehicle is a skid steer loader. The non-extended orretracted configuration of the skid steer loader body is essentially thesame as the configuration of known skid steer loaders. Thus theadvantageous features of conventional loaders are retainednotwithstanding the application of the invention to the vehicle.

It will be understood that more than one extension assembly may beutilised with the vehicle. As with a single extension assembly these maybe fitted inside the vehicle or mounted externally at the sides orunderneath the vehicle body.

It is envisaged that the invention can be applied to existing vehiclessuch as skid steer loaders and fork lifts by retrofitting namely bydividing part of the vehicle body and introducing an extension assemblyinto the vehicle.

Depending upon whether the vehicle to which the assembly is fitted isskid steer or conventional steer, the wheel drive arrangements mayrequire alteration to enable the extension assembly to be fitted to thevehicle so that each wheel may be driven separately or in pairs.

According to one form of the method aspect, the present inventioncomprises; a method for retrofitting an extension and retractionassembly to the body of a vehicle capable of receiving a work implement,the method comprising the steps of:

-   -   a) taking an existing vehicle,    -   b) dividing the vehicle body and/or chassis into two parts to        form body members or chassis parts,    -   c) inserting at least one extension assembly into the vehicle        having at least a fixed member which is fixedly attached to one        of the body members or chassis parts; and    -   d) a moveable member which moves within the fixed member and        which is engages directly or indirectly the other of the two        parts of the body or chassis whereupon the moveable member is        slideable within the fixed member,    -   e) installing control means in or on the body of the vehicle to        control extension and retraction of one body part relative to        the other part upon extension and retraction of said extension        assembly.

The extension assembly or assemblies may be themselves hydraulicallytelescopic or actuated by a telescopic hydraulic actuation cylinder andmay be themselves structural support beams which provide structuralrigidity to the body members. Preferably, the relative movement betweenthe body parts or sections is controlled hydraulically by the operatorof the machine. According to another embodiment the extension assemblymay be fitted to a fork lift vehicle.

The present invention will now be described in more detail according toa preferred but non-limiting embodiment and with reference to theaccompanying illustrations wherein:

FIG. 1 shows an isometric exploded view of a variable geometry vehiclein the expanded configuration according to a preferred embodiment of theinvention,

FIG. 2 shows an isometric view of the vehicle of FIG. 1 in theunexpanded configuration,

FIG. 3 shows from the front as located in a vehicle an abbreviatedportion of the hydraulic hose assembly which joins the pump and controlvalve and which extends and retracts responsive to extension andretraction of the vehicle,

FIG. 4 shows a side elevational view of the rear body member of FIG. 1depicting a hose guide,

FIG. 5 shows an isometric view of a skid steer loader in the unexpandedor retracted configuration according to a preferred embodiment of theinvention,

FIG. 6 shows the vehicle of FIG. 5 in the expanded configuration,

FIG. 7 shows an isometric view of a variable geometry vehicle having twotelescopic extension members,

FIG. 8 shows a schematic arrangement of the hydraulic system for avariable geometry vehicle with hydraulics to accommodate actuation of anextension assembly,

FIG. 9 shows a cross sectional plan view of a telescopic memberaccording to one embodiment;

FIG. 10 shows a cross sectional plan view of a telescopic memberaccording to a preferred embodiment;

FIG. 11 shows an isometric exploded view of a skid steer vehicle in theextended configuration wherein the rear body member and wheel assembliesmove relative to the drive motor;

FIG. 12 shows fully assembled, the vehicle of FIG. 11; and

FIG. 13 shows a side elevation of a fork lift vehicle according to analternative embodiment of the invention.

The present invention will now be described with reference to the abovefigures and particularly in its application to vehicles knowngenerically as skid steer loaders hereinbefore described. Although theinvention will be described with reference to skid steer and fork liftvehicles this is not to be construed as limiting of the applications ofthe invention.

A typical skid steer loader comprises a vehicle body mounted on a wheelassembly, a drive motor mounted in or on the body, a control cockpit,loader arms or other working attachment and a hydraulic system toactuate the working attachment.

Referring to FIG. 1 there is shown an isometric exploded view of atypical skid steer loader 1 having a body abbreviated for clarity.Vehicle body 2 is mounted on wheel assemblies 3 and 4 each of whichcomprises a pair of wheels attached at or near front and rear ends 5 and6 respectively of vehicle body 2. Skid steer loader bodies of the typeshown are generally of monocoque construction wherein the vehicle bodyacts as a chassis to which the wheel assemblies 3 and 4 are integrallymounted. According to a preferred embodiment, vehicle body 2 may begenerally divided into body members 7 and 8 each of which include wheelassemblies 3 and 4 respectively. The known vehicle bodies are integrallyconstructed and have no facility for extension in their length or forextension of the wheel base relative to or with part of the vehiclebody.

According to the embodiment shown, vehicle 2 has the ability to increaseits wheel base by virtue of an overall increase in the length of thevehicle body. The length increase is obtained by means of displacementof one body part relative to another body part. Thus, body member 8displaces relative to body member 7. The relative separation of bodymembers 7 and 8 is effected by means of an extension assembly 9.Extension assembly 9 includes a telescopic member 10 comprising a fixedfemale hydraulic member 11 and moveable member 12 responsive toactuation of the vehicle hydraulics. Preferably, the telescopic memberis cylindrical but it will be appreciated that the telescopic member canbe manufactured from alternative sections such as but not limited torectangular, square or diamond shape. Preferably, member 11 is fixedlyconnected to body member 7 so that it cannot move relative to bodymember 7. Moveable member 12 engages or is fixed to and moves with bodymember 8 and in view of the engagement which may be rigid fixationbetween member 12 and body 8 when the extension assembly 9 is actuated,member 12 causes body member 8 to displace in a rearward direction andaway from body member 7. Fixed member 11 may be bolted, screwed, weldedor otherwise connected to body member 7. Likewise for moveable member 12it may be bolted, welded or screwed or otherwise connected to bodymember 8. Extension assembly 9 operates in response to the vehiclesdrive system which includes drive motor 13. Drive motor 13 providesdrive to hydraulic piston pumps 13a and hydraulic ancillary pump 14.Hydraulic piston pumps 13a engage a network of hydraulic hoses whichtravel from the pump to the wheel motors to provide drive for thewheels. Pump 14 provides hydraulic power via a control valve to theextension assembly 9 enabling movement of body member 8 relative to bodymember 7 upon actuation by an operator of an actuation switch (notshown). Each wheel of wheel assemblies 3 and 4 comprise a wheel motor 15which transfers drive to the associated wheel. There are three wheelmotors depicted in FIGS. 15a, 15b and 15c with the remaining fourthwheel motor not shown for clarity. Due to the capability of vehicle body1 to undergo extension and retraction, it is necessary to providehydraulic hoses associated with the hydraulics which accommodate theextension. To this end, there are provided hoses 16 and 17 havingadditional length to accommodate extension in the vehicle and which passbetween hydraulic piston pumps 13a and wheel motors 15. Likewise, hoses18 and 19 are of sufficient length to undergo extension upon extensionof body member 8 relative to body member 7. In order to accommodate theadditional length when the vehicle is in the extended configuration,hoses 16, 17, 18 and 19 travel in guides which facilitate easy unrollingand rolling of the hoses (see FIG. 3). In addition to the extendablehoses there are hoses 20 and 21 which span between hydraulic pistonpumps 13a and wheel motor 15. Hoses 20 and 21 are of fixed length asbody member 8 preferably supports the drive assembly which includesdrive motor 13 and hydraulic pumps 13a and 14. Thus, in a preferredembodiment, the motor and pumps move rearwardly with the rearwardmovement of body member 8 in response to actuation of extension assembly9. In the embodiment where drive motor 13 and the associated pumps 13aand 14 are able to move rearward, the motor provides additionalcounterbalance for loads applied to the front end of the vehicle.According to an alternative embodiment, motor 13 and hydraulic pumps 13aand 14 are fixedly attached to member 7 such that body member 8 movesrelative to body member 7 and also relative to pumps 13a and 14 anddrive motor 13 (see description of FIG. 11).

FIG. 2 shows the vehicle of FIG. 1 in the retracted configurationwherein body members 7 and 8 are shown in abutting relationship. In FIG.2 it can be seen that the vehicle when retracted conforms to the shapeof a conventional vehicle of this type and that the extension assembly 9is fully concealed within the vehicle. When the vehicle is to bereturned from the extended configuration to the retracted configurationthe operator actuates the vehicle hydraulics and this causes actuationof the extension assembly 9. The retraction of the extension assembly 9enables moveable member 12 to travel through fixed member 11 (the latteracting as a support guide) and terminating at the front end of thevehicle body i.e. at body member 7.

FIG. 3 shows an enlarged front end abbreviated view of the arrangementsfor furling and unfurling the hoses 16 and 17. Hoses 16 and 17 travel inspecially fabricated upper and lower channels 22 and 23 respectively.Channel 23 is preferably welded to body member 7 and channel 22 isattached to body member 8. Each of channels 22 and 23 assist in guidinghoses 16 and 17 during extension and retraction of the vehicle.Likewise, hoses 18 and 19 are accommodated in a similar manner.Similarly, other components of the vehicle must be able to expand andretract and for this purpose other vehicle items (not shown) such aswiring fuel lines and control mechanisms for the hydrostatictransmission must have roll out roll in capability.

FIG. 4 shows a side elevational view of a body member 8 exploded fromthe vehicle of FIG. 1. This illustrates the relationship of channel 22to body member 8 as shown in abbreviated form in FIG. 3. FIG. 4 alsoshows motor 13 connected to pumps 13a, ancillary pump 14 and moveablemember 12.

Preferably the monocoque vehicle body is divided in such a way that twoprimary body members are formed. According to the preferred embodimentextension assembly 9 is located along the mid line of the vehicle whenonly one extension assembly is used. Where two or more extensionassemblies are used it is preferably that these be located symmetricallyabout the longitudinal axis to prevent the possibility of binding duringthe extension phase. Each of the wheels which comprise wheel assemblies3 and 4 are separately driven by means of separate drive motors whichare linked to the vehicle hydraulics. Extension assembly 9 may eitherhave its own hydraulic reservoir and associated actuation means or itmay simply be incorporated into the vehicles existing hydraulic system.

FIG. 5 shows a rear perspective view of a typical skid steer loader 30in unexpanded configuration including front end bucket 31 and associatedlifting arms 32. This vehicle is shown in the retracted configurationand when in this configuration has the appearance of a conventional skidsteer loader.

When a circular telescopic member as is depicted for extension assembly9 (see FIG. 1), there is a potential for rotational instability. Inorder to overcome this problem roller guides 24 and 25 are providedwhich accommodate rollers connected to body member 8. For clarity, FIG.1 shows roller assembly 26 but does not show the roller assembly whichtravels in roller guide 24. This interaction between roller guides andcorresponding roller assemblies prevent any unwanted rotation of bodymember 8 in relation to body member 7. Roller assembly 26 and thecorresponding roller assembly which travels in roller guide 24 mayinclude horizontal rollers which improve lateral stability.

Referring now to FIG. 6 there is shown vehicle 30 of FIG. 5 in theextended configuration. From this view it can be seen that body member34 is moved rearwardly in the direction of arrow 35 relative to bodymember 33. Body member 34 includes housing 36 which houses the majorparts of the vehicle drive assembly including the drive motor andhydraulic transmission and hydraulic pump. The rearward movement of bodymember 34 in this way provides a counter balance for loading applied tobucket 31 and hence provides a high resistance against overturninglongitudinally. When the vehicle is retracted as shown in FIG. 4 thevehicle retains all the characteristics of the prior art vehicle andthus the arrangements which enable extension of the vehicle arevirtually fully concealed from view.

FIG. 7 shows a rear schematic isometric view of a variable geometryvehicle having two telescopic extension members. Skid steer vehicle 40comprises body member 42, wherein body member 42 moves rearwardlyrelative to body member 41 in response to dual extension assemblies 43and 44. Where dual extension assemblies are shown it is preferable thatthese be disposed symmetrically about the longitudinal mid line of thevehicle to ensure that binding is prevented during the extension phase.The extension assemblies 43 and 44 operate in a similar manner for thatdescribed for extension assembly 9 shown in the vehicle in FIG. 1.

Due to the displacement of body member 8 relative to body member 7 asshown in FIG. 1, the wheel base of the vehicle is extended rendering thevehicle more stable during use. Also contributing to the counterbalanceof the vehicle is not only the rearward movement of the rear wheelassemblies but also the rearward movement of the drive assemblyincluding the drive motor 13 and associated hydraulic transmission andpumps 13a and 14 respectively.

FIG. 8 shows a schematic arrangement of the hydraulic system for avariable geometry vehicle with hydraulics to accommodate actuation of anextension assembly.

Referring to FIG. 9 there is shown a cross sectional plan view of atelescopic member 60 according to one embodiment. According to thisembodiment the telescopic member provides the structural strengthrequired for the extension and retraction facility. Member 60 comprisesmember 61 which is fixedly attached to the body of a vehicle. This actsas the fixed member of the telescopic member whilst member 62 movestelescopically and relative to member 61. Member 62 attaches to the bodymember of the vehicle which displaces. Member 60 further comprises oilgallery 63, guide block 64 and (hidden) piston and seals 65 and 66. Atend 67 of member 61 there are provided cylinder seals 68 and 69.

FIG. 10 shows a cross sectional plan view of a telescopic memberaccording to a preferred embodiment. The telescopic member 70 comprisesa female hydraulic cylinder 72, which houses hollow rod guides 73a and73b. Guides 73a and 73b are the principal support contact areas ofhollow rod 71. All radial movement of hollow rod 71 is controlled byguides 73a and 73b, while allowing and providing slideable contact areasfor the relative movement between hollow rod 71 and female cylinder 72.Fixedly attached to hollow rod 71 is (hidden) piston and piston seals74, and upon the introduction of hydraulic fluid, with pressure throughinlet or outlet ports of either 75a or 75b the said fluid pressure,acting on the piston 74 thereby causes relative movement between femalecylinder 72 and 71. Guides 73a and 73b incorporate identical sealingtechniques used in conventional cylinders.

The telescopic members of FIGS. 9 and 10, in addition to providing theextension capability for the vehicle to which these may be attached,also provide a rigid structural member which imparts structural rigidityto the vehicle particularly when in the extended configuration. In theunextended and extended configuration the structural telescopic memberalso provides junction between the main body members of the vehicle.

FIG. 11 shows an isometric exploded view of a skid steer vehicle in theextended configuration wherein the rear body member and wheel assembliesmove relative to the drive motor. The vehicle 80 of FIG. 11 is similarin general respects to the embodiment shown in FIG. 1 but this time therearward extension of the body member 81 is independent of the drivemotor 82. Thus, body member 81 moves rearwardly whilst motor 82 remainsfixed in position and attached directly to body member 83. The extensionof rear body member 81 includes movement rearward of wheel assemblies 83and 85 which are integral with body member 81. Wheel motor 85a is shownin conjunction with wheel assembly 85. Extension assembly 86 operates asa structural beam in a similar manner for that described with referenceto the corresponding extension assembly 9 for the vehicle of FIG. 1.When the rear body member 81 extends relative to body member 83 andmotor 82 additional counterbalance is provided for loads applied at thefront of the vehicle albeit less than the counterbalance provided whenthe motor also moves rearward as described with reference to FIG. 1.

FIG. 12 shows the vehicle 80 of FIG. 11 fully assembled.

FIG. 13 shows a side elevational view of a fork lift vehicle 90 to whichis adapted the extension and retraction facility according to analternative embodiment of the invention. Fork lift vehicle 90 comprisesa body 91 over which is placed a control cabin 92. Fork lift vehiclesusually comprise a fork lift assembly 93 comprising a generally uprightmainframe structure 94 and lifting forks 95. These are usually operatedhydraulically and apply significant load forward of the front wheel axis101. In normal use, this can create a tendency for the fork lift vehicleto overturn longitudinally and requires operator skill to ensure thatthe machine is kept in balance. Traditionally, as with short wheel basevehicles, in stability is a complication for an operator to deal with.By incorporating the extension assembly and the ability to increase thewheel base of the fork lift, the stability of the vehicle isdramatically improved due to additional counterbalance particularly whenforks 95 are under load. Fork lift 90 includes moveable member 96 whichis able to move rearward in the direction of arrow 97 and forwards inthe direction of arrow 98 when the vehicle is to be restored to itsoriginal configuration. As a result of the inclusion of the extensionassembly (not shown in FIG. 9) the vehicles wheel base can be extendedfor distances up to 1200 mm and beyond within reasonable limits. Thepositioning of body member 96 is determined by the operator according tothe amount of counterbalance required to overcome any tendency tooverturn longitudinally induced by loading on forks 95. Body member 96includes thereon drive motor 99 and associated hydraulic pumps (notshown) along with rear wheels 100 and associated mechanisms (not shown)and counterweight 101. Each of these members of the body member 96provide additional counterbalance when the vehicle is in the extendedconfiguration for loads lifted by forks 95. With this arrangement thevehicle is provided with improved stability and increased versatility inperforming functions which could not be safely performed when thevehicle is in the unextended configuration.

The foregoing description with reference to FIG. 1 describes themovement of body member 8 relative to body member 7. It will beappreciated that the vehicle could be redesigned such that the bodymember 7 moves relative to body member 8. In this configuration, member11 of telescopic member 10 would be fixedly attached to body part 8 andmember 12 would be connected to body member 7 being the moveable memberand would allow relative movement of body member 7 relative to bodymember 8. This also applies to the alternative embodiments of theinvention described herein.

In an alternative embodiment the telescopic member adapted for use withthe extension assembly may comprise a telescopic structural beampreferably of generally square or rectangular cross section which isfixed to the body members and contains a hydraulic cylinder thereinwhich operates in response to the drive assembly to facilitate movementof a moveable member which travels inside the beam.

During use, the operator selects the desired distance apart for bodymembers 7 and 8 (see FIG. 1) and this is generally determined accordingto use conditions. For instance, where a load is heavy or is carriedhigh by a front end loading implement, body members 7 and 8 will be atmaximum extension to resist instability and particularly the tendency tooverturn when climbing slopes. The operator may adjust the speed atwhich the extension and retraction takes place. Thus, the speed isadjustable and pre-set before the extension takes place or it may beadjusted at any time during the extension and retraction operation. Theadjustment is ideally effected by a flow control valve and may fallwithin the range 0.001 cm per second up to 1 meter per second accordingto requirements. Speeds outside this range are also possible.

According to an alternative embodiment, the telescopic member maycomprise a steel box section or alternatively a circular section. Thesize of the extension assembly can be altered according to the size ofthe machine although where the invention is applied to a skid steerloader an ideal size for the telescopic member would either be 150 mm indiameter or if a box section is used, 150 mm by 150 mm. It is envisagedthat the vehicle can be extended a number of feet and preferably over arange of between 0 to 1200 mm although larger extensions are feasible.

When the wheel base is fully extended loads applied to the front end ofthe vehicle are more effectively counterbalanced enabling the machine topick up more weight and consequently operate with a larger bucketcompared to the maximum bucket and load capability for the conventionalskid steer loader. One advantage of the variable geometry vehicle isthat due to the particular type of variable geometry applied inaccordance with the invention a smaller vehicle with a wider capabilitycan be used as a substitute for a larger vehicle. Furthermore, due tothe extension of the wheel base, greater traction is achieved so that inthe event that the vehicle became bogged in sandy or muddy ground anoperator can instantly adjust the wheel base transferring the loading onthe machine and the position of engagement between the tires and theground surface to facilitate extraction of the machine.

The working flexibility of the invention is manifested in being able toretract rapidly when turning, and extend rapidly when additionalstability is required when loading, climbing or simply travelling acrossdifficult terrain.

It will be recognised by persons skilled in the art that numerousvariations and modifications may be made to the invention withoutdeparting from the overall spirit and scope of the invention as broadlydescribed herein.

1. A mobile vehicle for lifting a load, comprising: a vehicle bodyincluding front and rear wheel assemblies each including at least a pairof wheels supporting respective front and rear vehicle body parts; animplement attached to the vehicle body for lifting said load; a drivemotor and controlling hydraulic pump mounted on the vehicle to said rearvehicle body part such that a substantial portion of the vehicle weightis carried by the rear vehicle body part of the vehicle; an independentextension and retraction assembly responsive to actuation of the drivemotor and mounted within said vehicle body; a controller for actuatingthe extension and retraction assembly responsive to an input from anoperator of the vehicle; wherein the extension and retraction assemblyallows the vehicle to move between a retracted state in which theextension and retraction assembly is fully retracted and the body partsare in opposition and where a wheel base distance is at a minimum forthe vehicle and an extended state in which the extension and retractionassembly is fully extended so that the body parts are at least partiallyseparated and the wheel base is set at a maximum for the vehicle;wherein, when the vehicle is extended, one wheel assembly supporting oneof said body parts is displaced relative to the other wheel assemblysupporting the other body part, the drive motor providing counterbalancefor said load and resistance against overturning under said load,;wherein at least one wheel of one or both said front wheel assembliesassembly includes at least one an independent hydraulic wheel motor andwherein a hydraulic network is provided comprising a plurality ofhydraulic hoses and one or more associated hose guides in which saidhoses travel to accommodate displacement of the body parts between asaid controlling pump mounted on one of the front and rear body partspart and said at least one wheel motor displace to accommodatedisplacement of the body parts of said front wheel assembly.
 2. Avehicle according to claim 1 wherein the front and rear body parts eachreceive a member of said extension assembly such that actuation of theextension assembly causes displacement of the rear body part of thevehicle relative to the front body part.
 3. A vehicle according to claim2 wherein the front and rear wheel assemblies support the respectivefront and rear body parts and wherein the drive motor is mounted on therear body part and moves with said rear body part.
 4. A vehicleaccording to claim 3 wherein the extension assembly comprises ahydraulically operated telescopic member having a fixed member fixed tothe front body part and a movable member fixed to the rear body part. 5.A vehicle according to claim 1 further comprising said controlling pumpbeing a hydraulic pump driven by the drive motor and being linked to theextension assembly via hydraulic hoses in communication with at leastone control valve.
 6. A vehicle according to claim 5 wherein thehydraulic hoses between said hydraulic pump and control valve move toaccommodate displacement of said rear body part.
 7. A vehicle accordingto claim 6 wherein two fixed hydraulic hoses link the control valve tothe telescopic member forming the extension and retraction assembly. 8.A vehicle according to claim 7 wherein the telescopic member includestherein a hydraulic cylinder which extends and retracts to facilitateextension and retraction of said extension assembly.
 9. A vehicleaccording to claim 8 wherein each body part includes two independentlydriven wheels.
 10. The vehicle of claim 1, wherein said extension andretraction assembly is mounted entirely within, without protrudingupwardly from, the vehicle body.
 11. A vehicle for lifting loads,comprising: a vehicle body comprising front and rear body parts;carriage means for said vehicle body comprising front and rear wheelassemblies, each including at least a pair of wheels; a drive motormounted on the vehicle to said rear body part such that a substantialportion of the weight of said drive motor is carried by said rear bodypart of said vehicle; a load lifting implement attached to said body forlifting said loads; an extension and retraction assembly responsive tothe drive motor and fitted within the body of the vehicle therebyallowing the vehicle to move responsive to an input from an operator ofthe vehicle between a retracted state in which a wheel base of thevehicle is at a minimum and the extension and retraction assembly isfully retracted, and an extended state where the wheel base distance isat a maximum and the extension and retraction assembly is fullyextended; wherein said extension and retraction assembly furthercomprises a pair of spaced generally parallel telescoping membersmounted within the vehicle body connected to extend and retract saidwheel base; wherein in said extended state the rear wheel assembly isrearwardly displaced relative to the front wheel assembly, wherein theextension and retraction assembly causes the vehicle body to part intofront and rear body parts each of which are connected to the extensionand retraction assembly and which are supported by the front and rearwheel assemblies respectively; wherein the drive motor moves with therear body thereby providing counter balance against vehicle instability,wherein each wheel includes a wheel motor and hydraulic hoses between acontrolling hydraulic pump located on one of said front and rear bodyparts and at least one pair of wheel motors moves to accommodatedisplacement of the moveable body parts.
 12. A vehicle according toclaim 11 wherein the hydraulic pump is driven by the drive motor and islinked to the extension assembly via hydraulic hoses which join the pumpto control a valve.
 13. A vehicle according to claim 12 where thehydraulic hoses between the pump and control valve move to accommodatedisplacement of said rear body relative to the front body part.
 14. Thevehicle of claim 11, wherein said extension and retraction assembly ismounted entirely within, without protruding upwardly from, the vehiclebody.
 15. A skid steer vehicle according to claim 14 wherein the frontand rear parts body together form the vehicle body each of which bodyparts are attached to a member of said extension assembly such thatactuation of the extension assembly causes longitudinal displacement ofthe rear part relative to the front body part.
 16. A skid steer vehicleaccording to claim 15 wherein the extension assembly includes at leastone telescopic member having one member fixed to the front body part anda moveable member fixed to the rear body part, wherein the telescopicmember is hydraulically operated.
 17. The vehicle of claim 11, whereinsaid vehicle is a skid steer vehicle.
 18. A mobile vehicle for lifting aload, comprising: a vehicle body including front and rear vehicle bodyparts each including and supported by a separate wheel assembly, eachwheel assembly including at least a pair of wheels, each of said wheelsbeing coupled to a wheel motor; an implement attached to the vehiclebody for lifting said load; an extension and retraction assembly coupledto said front and rear vehicle body parts and mounted within saidvehicle body; wherein, when the vehicle is extended, one wheel assemblysupporting one of said body parts is displaced relative to the otherbody part; a controller in communication with at least one control valvefor actuating the extension and retraction assembly in response to aninput from an operator of the vehicle; a drive motor mounted on the rearvehicle body part of the vehicle body and coupled to a plurality ofhydraulic pumps, the drive motor and pumps being positioned such that asubstantial portion of their combined weight is carried by the rearvehicle body part, the weight of said drive motor and said plurality ofpumps providing counterbalance for said load and resistance againstoverturning of the vehicle under said load; a network of hoses linked tosaid at least one control valve for carrying hydraulic fluid between atleast one of said pumps and said extension and retraction assembly suchthat said extension and retraction assembly is responsive to actuationof said controller thereby causing the drive motor and said at least oneof said pumps to displace the wheel assemblies supporting said front andrear vehicle body parts with respect to each other and move said frontand rear vehicle body parts between a retracted state in which theextension and retraction assembly is fully retracted and the body partsare in opposition and where a wheel base distance is at a minimum forthe vehicle and an extended state in which the extension and retractionassembly is fully extended so that the body parts are at least partiallyseparated and the wheel base is set at a maximum for the vehicle; anetwork comprising a plurality of hydraulic hoses for carrying hydraulicfluid between at least one of said pumps and each of said wheel motorsto provide drive for the wheels, said network of hoses carryinghydraulic fluid between said pumps and each of said wheel motors of saidfront wheel assembly being long enough to undergo displacement uponactuation of the extension and retraction assembly to accommodate themaximum and minimum wheel base of the vehicle and associated hose guidesin which said hoses travel are provided.
 19. A mobile vehicle forlifting a load, comprising: a vehicle body including front and rear bodyparts respectively supported by front and rear wheel assemblies eachassembly including at least a pair of wheels for support; an implementattached to the front body part of the vehicle body for lifting saidload; a drive motor and controlling hydraulic pump mounted on said rearvehicle body part of the vehicle such that a substantial portion of thecombined weight of said drive motor and controlling pump is carried bythe rear vehicle body part of the vehicle; wherein at least one wheel ofone or both said wheel assemblies includes at least one wheel motor andwherein hydraulic hoses between said controlling pump mounted on saidrear body part and said at least one wheel motor displace to accommodatedisplacement of the body parts; an extension and retraction assembly,including at least one telescopically deployed member mounted within thevehicle body, responsive to actuation of the drive motor and mountedwithin said vehicle body; a controller for actuating the extension andretraction assembly responsive to an input from an operator of thevehicle; wherein the extension and retraction assembly allows thevehicle to move between a retracted state in which the extension andretraction assembly is fully retracted and the body parts are inopposition and where a wheel base distance is at a minimum for thevehicle and an extended state in which the extension and retractionassembly is fully extended so that the body parts are at least partiallyseparated and the wheel base is set at a maximum for the vehicle;wherein, when the vehicle is extended, one wheel assembly supporting oneof said body parts is displaced relative to the other wheel assemblysupporting the other body part, the drive motor providing counterbalancefor said load and resistance against overturning under said load;wherein a hydraulic network is provided comprising a plurality ofhydraulic hoses and one or more associated hose guides in which saidhoses travel to accommodate displacement of the body parts between saidcontrolling pump mounted on the rear body part and said at least onewheel motor of said front wheel assembly.
 20. A mobile vehicle forlifting a load, comprising: a vehicle body including a front wheelassembly each including at least a pair of wheels supporting respectivefront and rear vehicle body parts and a rear assembly including at leasta pair of wheels supporting the rear vehicle body parts; an implementcomprising a fork lift arm or other mountable device attached to thevehicle body for lifting said load; a drive motor and controlling pumpmounted on said rear vehicle body part of the vehicle such that asubstantial portion of the combined weight of said drive motor andcontrolling pump is carried by said rear vehicle body part and whereinthe motor and controlling pump act as a counter balance weight to saidload when said load is lifted by the implement; wherein at least onewheel of one or both said wheel assemblies includes at least one wheelmotor and wherein hydraulic hoses between said controlling pump mountedon said rear body part and said at least one wheel motor displace toaccommodate displacement of the body parts; an extension and retractionassembly responsive to actuation of the drive motor and mounted withinsaid vehicle body; a controller for actuating the extension andretraction assembly responsive to an input from an operator of thevehicle; wherein the extension and retraction assembly allows thevehicle to move between a retracted state in which the extension andretraction assembly is fully retracted and the body parts are inopposition and where a wheel base distance is at a minimum for thevehicle and an extended state in which the extension and retractionassembly is fully extended so that the body parts are at least partiallyseparated and the wheel base is set at a maximum for the vehicle;wherein, when the vehicle is extended, one wheel assembly supporting oneof said body parts is displaced relative to the other wheel assemblysupporting the other body part, the drive motor providing counterbalancefor said load and resistance against overturning under said load;wherein a hydraulic network is provided comprising a plurality ofhydraulic hoses and one or more associated hose guides in which saidhoses travel to accommodate displacement of the body parts between saidcontrolling pump mounted on the rear body part and said at least onewheel motor of said front wheel assembly.
 21. A vehicle according toclaim 1 wherein at least one of the hydraulic hoses of the extension andretract assembly travels in a fabricated channel.
 22. A vehicleaccording to claim 21 wherein the fabricated channels guide the hosesduring extension and retraction by facilitating easy unrolling androlling of the hoses.
 23. A vehicle according to claim 1 wherein theimplement comprises a fork lift.
 24. A vehicle according to claim 1wherein the implement comprises a lift arm and bucket arrangement.
 25. Avehicle according to claim 1 wherein the extension and retractionassembly further comprises a telescoping member mounted within thevehicle body and further comprising symmetrically located assembliesgenerally parallel to said extension and retraction assembly to overcomerotational instability.
 26. A vehicle according to claim 1 wherein anamount of extension is variable based on loading.